226 - Effect of lewis acids on the electrochemical reduction of nicotinamide adenine dinucleotide

Electrochemically, nicotinamide adenine dinucleotide (NAD+; DPN+; coenzyme I) is reduced in two steps, i.e., a pH-independent one-electron reduction to the free radical, which, at more negative potential, is reduced in a one-electron, one-proton process to NADH. The variation in the electrochemical pattern resulting from interaction with two acids known to be involved biologically with NAD+ i.e., Ca(II) and Zn(II), has been examined. Potentiometric titration indicates that Ca(II) forms a weak 1:1 complex with NAD+ at pH 7.2 (formation constant equals 38); d.c. polarography supports such complexation. The nature and effects of these complexes have been explored, e.g., Ca(II) increases the rate of charge transfer to that expected for a reversible reaction for the first reduction step only at relatively high concentration but has a marked effect on the second step even at low concentration. Zn(II) apparently forms a complex with a decomposition product of NAD+, which catalyzes the Zn(II) reduction.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22742/1/0000297.pd

244 - Oxidation of 1,4-NADH at a glassy carbon electrode: effects of pH, Lewis Acids and Adsorption

The effects of pH, acids [Ca(II); Zn(II)] and adsorption on the electrochemical oxidation of dihydronicotinamide adenine dinucleotide (1,4-NADH) at a glassy carbon electrode have been investigated in aqueous media using cyclic voltammetry. The oxidation of NADH to NAD+ (nicotinamide adenine dinucleotide) is highly irreversible and is only marginally dependent on pH; the initial charge transfer is indicated to be rate-controlling step. Oxidation of at least some of the NADH as an adsorbed species makes the oxidation more difficult, as does the presence of Ca(II) and Zn(II); the possible causes for this behavior are examined.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22751/1/0000306.pd

Probability Aggregation in Time-Series: Dynamic Hierarchical Modeling of Sparse Expert Beliefs

Most subjective probability aggregation procedures use a single probability judgment from each expert, even though it is common for experts studying real problems to update their probability estimates over time. This paper advances into unexplored areas of probability aggregation by considering a dynamic context in which experts can update their beliefs at random intervals. The updates occur very infrequently, resulting in a sparse data set that cannot be modeled by standard time-series procedures. In response to the lack of appropriate methodology, this paper presents a hierarchical model that takes into account the expert’s level of self-reported expertise and produces aggregate probabilities that are sharp and well calibrated both in- and outof-sample. The model is demonstrated on a real-world data set that includes over 2300 experts making multiple probability forecasts over two years on different subsets of 166 international political events

Comparative adsorption of adenine and nicotinamide adenine dinucleotide (NAD+) at an aqueous solution | mercury interface

The relative extent of adsorption of adenine and NAD+ at the 10-[mu]M level from a solution of pH 4.8 and 0.5 M ionic strength (McIlvaine buffer) has been measured as a function of potential by an inverse normal pulse polarographic technic at a dropping mercury electrode (d.m.e.). Normalization of the pulse polarographic current resulting from pre-concentration of the electroactive species through adsorption compared to the current expected for a simple diffusion-controlled electron-transfer indicates that NAD+ is strongly adsorbed over a broader potential range than adenine, and that its surface concentration is slightly greater; causes for such behavior are considered. Other normalization approaches indicate NAD+ to be strongly adsorbed but comparably to adenine when account is taken of the relative effective areas occupied on adsorption.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25046/1/0000474.pd

Stability and Instability of Relativistic Electrons in Classical Electro magnetic Fields

The stability of matter composed of electrons and static nuclei is investigated for a relativistic dynamics for the electrons given by a suitably projected Dirac operator and with Coulomb interactions. In addition there is an arbitrary classical magnetic field of finite energy. Despite the previously known facts that ordinary nonrelativistic matter with magnetic fields, or relativistic matter without magnetic fields is already unstable when the fine structure constant, is too large it is noteworthy that the combination of the two is still stable provided the projection onto the positive energy states of the Dirac operator, which defines the electron, is chosen properly. A good choice is to include the magnetic field in the definition. A bad choice, which always leads to instability, is the usual one in which the positive energy states are defined by the free Dirac operator. Both assertions are proved here.Comment: LaTeX fil

Breadth of antibodies to Plasmodium falciparum variant surface antigens is associated with immunity in a controlled human malaria infection study

Background: Plasmodium falciparum variant surface antigens (VSAs) contribute to malaria pathogenesis by mediating cytoadhesion of infected red blood cells to the microvasculature endothelium. In this study, we investigated the association between anti-VSA antibodies and clinical outcome in a controlled human malaria infection (CHMI) study. Method: We used flow cytometry and ELISA to measure levels of IgG antibodies to VSAs of five heterologous and one homologous P. falciparum parasite isolates, and to two PfEMP1 DBLβ domains in blood samples collected a day before the challenge and 14 days after infection. We also measured the ability of an individual’s plasma to inhibit the interaction between PfEMP1 and ICAM1 using competition ELISA. We then assessed the association between the antibody levels, function, and CHMI defined clinical outcome during a 21-day follow-up period post infection using Cox proportional hazards regression. Results: Antibody levels to the individual isolate VSAs, or to two ICAM1-binding DBLβ domains of PfEMP1, were not associated with a significantly reduced risk of developing parasitemia or of meeting treatment criteria after the challenge after adjusting for exposure. However, anti-VSA antibody breadth (i.e., cumulative response to all the isolates) was a significant predictor of reduced risk of requiring treatment [HR 0.23 (0.10-0.50) p= 0.0002]. Conclusion: The breadth of IgG antibodies to VSAs, but not to individual isolate VSAs, is associated with protection in CHMI

Functional alpha-1B adrenergic receptors on human epicardial coronary artery endothelial cells

Alpha-1-adrenergic receptors (α1-ARs) regulate coronary arterial blood flow by binding catecholamines, norepinephrine (NE), and epinephrine (EPI), causing vasoconstriction when the endothelium is disrupted. Among the three α1-AR subtypes (α1A, α1B, and α1D), the α1D subtype predominates in human epicardial coronary arteries and is functional in human coronary smooth muscle cells (SMCs). However, the presence or function of α1-ARs on human coronary endothelial cells (ECs) is unknown. Here we tested the hypothesis that human epicardial coronary ECs express functional α1-ARs. Cultured human epicardial coronary artery ECs were studied using quantitative real-time reverse transcription polymerase chain reaction, radioligand binding, immunoblot, and 3H-thymidine incorporation. The α1B-subtype messenger ribonucleic acid (mRNA) was predominant in cultured human epicardial coronary ECs (90–95% of total α1-AR mRNA), and total α1-AR binding density in ECs was twice that in coronary SMCs. Functionally, NE and EPI through the α1B subtype activated extracellular signal-regulated kinase (ERK) in ECs, stimulated phosphorylation of EC endothelial nitric oxide synthase (eNOS), and increased deoxyribonucleic acid (DNA) synthesis. These results are the first to demonstrate α1-ARs on human coronary ECs and indicate that the α1B subtype is predominant. Our findings provide another potential mechanism for adverse cardiac effects of drug antagonists that nonselectively inhibit all three α1-AR subtypes

Performance of Monolayer Graphene Nanomechanical Resonators with Electrical Readout

The enormous stiffness and low density of graphene make it an ideal material for nanoelectromechanical (NEMS) applications. We demonstrate fabrication and electrical readout of monolayer graphene resonators, and test their response to changes in mass and temperature. The devices show resonances in the MHz range. The strong dependence of the resonant frequency on applied gate voltage can be fit to a membrane model, which yields the mass density and built-in strain. Upon removal and addition of mass, we observe changes in both the density and the strain, indicating that adsorbates impart tension to the graphene. Upon cooling, the frequency increases; the shift rate can be used to measure the unusual negative thermal expansion coefficient of graphene. The quality factor increases with decreasing temperature, reaching ~10,000 at 5 K. By establishing many of the basic attributes of monolayer graphene resonators, these studies lay the groundwork for applications, including high-sensitivity mass detectors

Metallicity Gradients at Large Galactocentric Radii Using the Near-infrared Calcium Triplet

We describe a new spectroscopic technique for measuring radial metallicity gradients out to large galactocentric radii. We use the DEIMOS multi-object spectrograph on the Keck telescope and the galaxy spectrum extraction technique of Proctor et al. (2009). We also make use of the metallicity sensitive near-infrared (NIR) Calcium triplet (CaT) features together with single stellar population models to obtain metallicities. Our technique is applied as a pilot study to a sample of three relatively nearby (<30 Mpc) intermediate-mass to massive early-type galaxies. Results are compared with previous literature inner region values and generally show good agreement. We also include a comparison with profiles from dissipational disk-disk major merger simulations. Based on our new extended metallicity gradients combined with other observational evidence and theoretical predictions, we discuss possible formation scenarios for the galaxies in our sample. The limitations of our new technique are also discussed.Comment: 13 Pages, 9 Figures, 7 Tables, Accepted for publication in MNRA